Chapter 6 & 9
Free Response Questions

Reminder: All illustrations need to be accompanied by text which explains them clearly. An illustration without accompanying text will receive no credit. This is the way the College Board does it. Also, I will not accept copy and pasted illustrations in any free response answers this year because I believe there is great value in creating them yourselves, i.e. you remember and understand them much better if you create them.

Note: All the answers can be found in either the text or the notes (or both). You need to be careful and thorough in writing your answers since the test key will be very specific.

1. Describe what an enzyme does, i.e. discuss how enzymes influence the activation energy of a reaction. Include a diagram of the energy profile of an exergonic reaction and how an enzyme modifies this profile (see fig. 6.10). Describe our current model of how enzymes work, i.e. the “Induced Fit Hypothesis”. Be sure to include a series of pictures and accompanying text that show how they work. Include a definition of the terms (within the context of the text): enzyme, substrate, active site, products, and reactants (see fig. 6.12) . Explain what kind of biochemical molecules enzymes are. Explain how enzymes acquire their unique structure and how this leads to their function in living systems. Explain why enzymes are important in biological systems, why they evolved in the first place. Distinguish between competitive and non-competitive inhibition. Illustrate the difference with a drawing (see fig. 6.14). Give an example of each. Discuss allosteric regulation of reactions and how enzymes are used in the homeostatic process of feedback inhibition. Draw a picture illustrating allosteric regulation and another illustrating feedback inhibition (see figures 6.15 and 6.16)

2. After an enzyme is mixed with its substrate, the amount of product
formed is determined at 10-second intervals for 1 minute. Data from this
experiment are shown below.

Time (sec) 0 10 20 30 40 50 60
Product formed (mg) 0.0 0.25 0.50 0.70 0.80 0.85 0.85

Draw a graph of these data (using graph paper) and answer the following questions. (Note: Time is always on the “x” axis whenever you graph something with time as a variable - remember this for the AP exam!)

a. What is the initial rate of this enzymatic reaction?
b. What is the rate after 50 seconds? Why is it different from
the initial rate?
c. What would be the effect on product formation if the enzyme
were heated to a temperature of 100oC for 10 minutes before
repeating the experiment? Why?
d. How might altering the substrate concentration affect the rate of
the reaction? Why?
e. How might altering the pH affect the rate of reaction? Why?

3. a. Diagram the overall simple chemical equation for respiration (end of first paragraph on page 148). Explain what it means in words.

b. Act One of the three part drama called, “Respiration”: Glycolysis
•Explain what the word glycolysis means- break it down into its roots- and then explain what it means.
•Identify where in the cell this occurs.
•Name what molecule “begins” the process of glycolysis and what molecule “ends” the process. List how many carbons are found in the beginning and ending molecule.
•What is the first half of glycolysis called? What results from the first half of the reaction? What molecules appear? List all the molecules that exist after the first half of glycolysis, their number and their significance (ADP, Glyceraldehyde Phosphate)
•What is the second half of glycolysis called? What results from the second half of the reaction? What molecules appear? List all the molecules that exist after the second half of glycolysis, their number and their significance (ATP, NADH, pyruvate).
•Show an overall energy budget for glycolysis (see figure 9.8)
•Explain the significance of the enzyme phosphofructokinase (see figure 9.20).

c. Act Two of the three part drama called, “Respiration”: Krebs Cycle
•Explain what the Krebs Cycle is, in general (one or two sentence summary).
•Discuss where in the cell the Krebs Cycle occurs.
•Diagram and explain what I call “The Bridge” (see figure 9.10).
•Identify how many carbons acetyl-Coenzyme A has.
•Name the first molecule in the cycle. Discuss how many carbons this molecule has.
•Give an overview of the whole cycle. Discuss the different molecules that are produced (NADH, FADH2, ATP, CO2) and in what quantity (for both the bridge and the actual cycle). (see figure 9.12)
•Discuss where the carbon for the carbon dioxide originally comes from.
•Do an overall energy budget for the Krebs Cycle and Glycolysis.

4. Act Three of the three part drama called, “Respiration”: Electron Transport Chain and Oxidative Phosphorylation.
•Act Three is driven by a process called Chemiosmosis. Explain what this is, in general (a short overview).
•Explain where in the cell this process occurs.
•Include a diagram of the mitochondria labeling where things happen. Explain how this mechanism uses NADH to produce ATP (see figure 9.15).
•Discuss the function of ATP Synthase (see figure 9.14)